1. Field of the Invention
The present invention relates to water treating devices and, more particularly, to a system in which hard water is softened and a reduction in the dissolved solids in the water is obtained.
2. Prior Art
Water softener systems presently in use are of the type in which hard, raw water enters the top of a pressure tank through an inlet line, percolates through a bed of treatment material, such as zeolite, and passes out of the pressure tank through an outlet line having a mouth located proximate the bottom of the tank. As the hard water percolates through the zeolite bed, an ion exchange occurs in which sodium ions held by the zeolite are exchanged for the "hard" metal ions in the water.
The water softening ability of the zeolite bed is gradually reduced through use and, after a predetermined quantity of hard water has been softened, the zeolite bed becomes depleted of sodium ions. The zeolite bed is thereafter regenerated by passing a brine solution through it so that the ion exchange process is reversed.
Reverse osmosis water treatment systems are known in the art in which water is filtered by passing through a semi-permeable membrane carried on a rigid structure, such as a perforated metal tube, and then is collected in a holding tank. Such a system is disclosed, for example, in U.S. Pat. No. 3,493,496, issued May 13, 1968, to Bray et al. Bray discloses a semi-permeable membrane element which comprises a porous fabric enclosed in a semi-permeable membrane material and wrapped in a spiral about a perforated tube. A plastic screen is positioned adjacent the membrane material so that it forms spaces between successive layers of the wrapped membrane to permit fluid flow across the surface of the wrapped membrane material.
The spirally wrapped membrane typically is positioned within a vessel and includes a fluid conduit connected to the perforated tube which conveys treated water to a holding tank or fluid dispensing means. The vessel also includes a raw water inlet and a bleed water outlet. Raw water washes past the membrane surface continually and is removed through the bleed water outlet carrying with it dissolved solids which could not pass through the semi-permeable membrane.
A disadvantage of typical reverse osmosis treatment systems is that small particulate contaminants may collect on the surfaces of the membranes to restrict the flow of fluid through the membrane material, thus necessitating a pretreatment filter. Such a filter may become clogged and, therefore, require cleaning from time to time. Furthermore, such water treatment systems require a pressure vessel for the reverse osmosis system which is separate from the remainder of the water treatment devices which may also be in use. This adds to the complexity, cost, and space required for the combined system.
Accordingly, there is a need for a water softening and treatment system in which hard, raw water is softened and dissolved solids or other impurities removed therefrom within a single pressure tank. Furthermore, there is a need for a water softening and treatment system which is relatively easy to maintain and in which a pretreatment filter is not required.